1. Field of the Invention
This invention relates to an electrically actuated wheel hub clutch apparatus and more particularly to an electrically actuated wheel hub clutch apparatus for automobiles and other types of machines.
2. Description of the Related Art
A conventional electric wheel hub clutch apparatus is disclosed in Japanese Utility Model Laid Open Publication No. 63(1988)-52626 published without examination on Apr. 8, 1988. The clutch is adapted to convert from two-wheel drive to fourwheel drive by turning a switch. That clutch is shown in FIG. 5, herein where a wheel hub 19' is rotatably assembled on an outer peripheral surface of a stationary axle tube 14' by means of bearings 30', 31'. A cylindrical body 1' is fixed to a cover 2' by a bolt 3'. A ring 4' is fixed to an inside portion of the cylindrical body 1' by a plate 9' and a snap ring 5'. An inner sleeve 6' which is rotated together with an axial shaft 8' is engaged with the snap ring 5a' and is rotatably supported by the ring 4'. A cam surface 12b' is formed on the outer peripheral surface of a boss 12a' of a handle 12'.
A clutch member 7' is in contact with a cam follower 10' assembled in the boss 12a'. The outer peripheral surface of the clutch member 7' and the inner peripheral surface of the cylindrical body 1' are axially and slidably attached by a spline-connection. A tension spring 13' is provided, between the clutch member 7' and the cam follower 10' and a tension spring 11' is provided between the handle 12' and the cam follower 10'. Furthermore, a motor 16' fixed in a lateral wall of the cylindrical body 1' has a shaft 16a' and a pinion gear 15' fixedly connected to a free end portion of the shaft member 16a'. Gear teeth 12c' are provided on the outer peripheral surface of the handle 12' so as to engage with the pinion gear 15'.
A lock plate 32' is in spline-connection with the axle tube 14' and a lock nut 33' is connected to the lock plate 32' by means of a bolt 34'. A pair of slip rings 35' are assembled on the outer periphery of the lock nut 32'. An electric cord 36' is inserted in a throughhole 14a' formed in the axle tube 14'. One end of the electric cord 36' is connected to a terminal of the slip ring 35', and other end of the electric cord 36' is connected to a control box (not shown), an electric source (not shown), and a switch of a driver's seat in the automotive vehicle. A brush case 37' is fixed to the wheel hub 19', and a pair of springs 38' are accommodated in the brush case 37'. A pair of brushes 39' are connected to ends of the springs 38' and are biased against the slip rings 35'. A convex terminal 16b' of the motor 16' is fixedly connected to a concave terminal 40' attached to other end of the springs 38'.
In operation, assume that the clutch member 7' is disengaged from the inner sleeve 6' as shown in FIG. 5. After the switch (not shown) is turned on, electric current flows to the motor 16' through the slip rings 35', and the shaft 16a' is rotated in one direction. The handle 12' engaged with the pinion gear 15' is rotated into the one direction, and a pawl 10a' of the cam follower 10' is leftwardly cammed by a cam surface 12b' of the handle 12'. Accordingly, the clutch member 7' is leftwardly moved and is engaged with the inner sleeve 6' via splines 6a', 7a'. The axle shaft 8' is thereby connected to the wheel hub 19' to perform the four-wheel drive function.
In the above-mentioned conventional free wheel hub apparatus, the lock plate 32' having the slip rings 35' is in spline-connection with the axle tube 14'. The brush case 37' having the brushes 39' contacted with the slip rings 35' is assembled in the wheel hub 19'. Thus, the lock plate 32' and the brush case 37' are separately provided so that the brushes 39' are influenced by the vibration of the condition of road surface through the wheel hub 19' and a wheel of the vehicle. Accordingly, there is the possibility that the brushes 39' may become shifted away from the contacting surface of the slip rings 35'. Furthermore, it is difficult to adjust the brushes 39' to the slip rings 35' upon assembling the brush case 37' and the slip rings 35', so that there is the possibility that the brushes 39' and the slip rings 35' become abnormally worn. As a result, there is a fear that the ability to transmit electric current is impaired due to the bad condition of the environment such as vibration and the presence of foreign materials, etc.